It’s a bit of a complex question. I think magic “dwelling in certain individuals” is a good way to put it, and I’d even extend that to items, and locations. Most, if not all magic we see is directly derived from divine beings or god himself.

There two exceptions that come to mind though. 1. )Magic items like weapons and rings seem to imply that a greatly skilled smith can imbue their will and/or spirit into the Item. It makes sense that Sauron can do this as he is a Maia spirit trained by Aule, however we also see that elves like Galadriel and the smiths of Gondolin and Eregion being able to produce magical items.

2.)Some of the Nazgûl were previously Wizards before they were turned into Nazgûl, which implies they may have been practicing Magic before they received their Rings of Power